@elunic/debug-levels

@elunic/debug-levels

Thin wrapper around the visionmedia/debug module, providing support for both:

• debug levels (fatal, error, warn, info, debug, trace)
• easy creation of child namespaces

The decision to write a new wrapper rather than use an existing one (such as debug-level, debug-levels) was made because of the requirement for child namespaces within the debug "namespace" concept. Currently, to our knowledge, no module providing both easy creation of child namespaces and debug levels exists.

Table of Contents

• Installation
• Log levels
• Usage
  • Child namespaces
  • Global API
  • Per-logger log level
  • Environment variables
• License

Installation

$ npm install @elunic/debug-levels

Log levels

@elunic/debug-levels provides the bunyan log levels: fatal, error, warn, info, debug, trace.

A description of these levels can be found on the bunan GitHub page.

Usage

@elunic/debug-levels, like debug, exposes a function, which takes one argument: the debug namespace.

Like debug, this returns a function which can be used to log. In contrast to debug, however, this logging function will log with the default logging level 'INFO'.

This is intended to make @elunic/debug-levels a progressive enhancement and drop-in replacement for debug.

Additionally, the returned function object has method properties for each logging level.

Example:

const logger = require('@elunic/debug-levels')('http');

logger('information about regular operation');
// INFO http information about regular operation

logger.fatal('unrecoverable error, an operator should look at this as soon as possible');
// FATAL http unrecoverable error, an operator should look at this as soon as possible

logger.error('recoverable error');
// ERROR http recoverable error

logger.warn('warning');
// WARNING http warning

logger.info('information about regular operation');
// INFO http information about regular operation

logger.debug('debug information, perhaps useful during development or troubleshooting');
// DEBUG http debug information, perhaps useful during development or troubleshooting

logger.trace('highly detailed information');
// TRACE http highly detailed information

Child namespaces

Each logger exposes a createLogger function, which creates a child namespace.

const logger = require('@elunic/debug-levels')('http');
const getLogger = logger.createLogger('get');

getLogger.info('200 /index.js');
// INFO http:get 200 /index.js

The same can be achieved through an initial declaration of the namespace using the debug syntax:

const getLogger = require('@elunic/debug-levels')('http:get');

However, using logger.createLogger() is useful if you do not want to repeat yourself by writing out the parent namespace throughout your module.

Global API

@elunic/debug-levels exposes the underlying debug API with two additions: setLevel() and getLevel(), used to set or get the current global debug level. Note that this level may be overriden on a per-logger basis using logger.setLevel().

For all other configuration options/APIs, consult the debug documentation. The API can be applied to debuglevels.debug (see below).

const debuglevels = require('@elunic/debug-levels');

// Output "warn" and above levels only
debuglevels.setLevel('warn');

debuglevels.getLevel();
// "warn"

// Convenience assignments
debuglevels.level = 'warn'; // set
debuglevels.level; // get

// debuglevels exposes debug's enable() and disable() methods
debuglevels.enable('http');
debuglevels.enable('http,socket.io');
debuglevels.enable('http:get');
debuglevels.enable('*');

// ... as well as the underlying debug object
debuglevels.debug.enable('http');

Per-logger log level

Each logger may have its debug level set on an individual basis. This setting overrides the global debug level, so it is possible to have a logger that logs everything on trace while the global level is set to fatal.

const debuglevels = require('@elunic/debug-levels');

const logger = debuglevels('http');
const getLogger = debuglevels('http:get');

debuglevels.setLevel('fatal');
getLogger.setLevel('trace');

// Silent
logger.info('generic http info');

// Produces output
getLogger.info('get request');

// Convenience assignments
getLogger.level; // get; "trace"
getLogger.level = 'trace'; // set

To remove a child logger's individual log level, call it with a falsy value:

getLogger.setLevel(null);

Environment variables

As a wrapper around debug, @elunic/debug-levels provides all its environment variables (see the debug documentation), with one addition: DEBUG_LEVELS.

DEBUG_LEVELS can be set to either of the supported debug levels.

Example usage:

DEBUG_LEVEL=debug DEBUG=* node index.js

License

(The MIT License)

Copyright (c) 2018 elunic <[e-mail]>

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the 'Software'), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED 'AS IS', WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.